/*
 * modbus_priv.h
 *
 * Change Logs:
 * Date           Author       Notes
 * 2022-01-25     nx           the first version
 *
 */

#include "modbus_utils.h"

#define _ntohl(x)    _bswap_32 (x)
#define _ntohs(x)    _bswap_16 (x)
#define _htonl(x)    _bswap_32 (x)
#define _htons(x)    _bswap_16 (x)

/* Table of CRC values for high-order byte */
static const mb_uint8_t table_crc_hi[] =
{
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40
};

/* Table of CRC values for low-order byte */
static const mb_uint8_t table_crc_lo[] =
{
    0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7,
    0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E,
    0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9,
    0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC,
    0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
    0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32,
    0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D,
    0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38,
    0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF,
    0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
    0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1,
    0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4,
    0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB,
    0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA,
    0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
    0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0,
    0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97,
    0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E,
    0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89,
    0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83,
    0x41, 0x81, 0x80, 0x40
};


static inline mb_uint16_t _bswap_16(mb_uint16_t x)
{
    return (x >> 8) | (x << 8);
}

static inline mb_uint32_t _bswap_32(mb_uint32_t x)
{
    return (_bswap_16(x & 0xffff) << 16) | (_bswap_16(x >> 16));
}

/**
  \brief  The function calculates CRC-16 check on a MODBUS_FRAME structure
*/
mb_uint16_t modbus_crc16(mb_uint8_t *frame, mb_uint16_t len)
{
    mb_uint8_t crc_hi = 0xFF;   /* high CRC byte initialized */
    mb_uint8_t crc_lo = 0xFF;   /* low CRC byte initialized */
    mb_uint32_t index;          /* will index into CRC lookup */

    /* pass through message buffer */
    while (len--)
    {
        index = crc_hi ^ *(frame++); /* calculate the CRC  */
        crc_hi = (mb_uint8_t)(crc_lo ^ table_crc_hi[index]);
        crc_lo = table_crc_lo[index];
    }

    return (mb_uint16_t)(crc_hi << 8 | crc_lo);
}

/**
  \brief  The function calculates an 8-bit Longitudinal Redundancy Check
          on a MODBUS_FRAME structure
*/
mb_uint8_t modbus_lrc(mb_uint8_t *frame, mb_uint16_t len)
{
    mb_uint8_t lrc = 0;  /* LRC char initialized */

    while (len--)
    {
        lrc += *frame++;   /* Add buffer byte without carry */
    }

    /* Return twos complement */
    lrc = (mb_uint8_t)(-((mb_uint8_t)lrc));
    return lrc;
}

/**
  \brief  Converts a ASCII characters to a byte.
*/
mb_uint8_t modbus_char_to_bin(mb_char_t character)
{
    if ((character >= '0') && (character <= '9'))
    {
        return (mb_uint8_t)(character - '0');
    }
    else if ((character >= 'A') && (character <= 'F'))
    {
        return (mb_uint8_t)(character - 'A' + 0x0A);
    }
    return 0xFF;
}

/**
  \brief  Converts a byte to ASCII characters.
*/
mb_char_t modbus_bin_to_char(mb_uint8_t byte)
{
    if (byte <= 0x09)
    {
        return (mb_char_t )('0' + byte);
    }
    else if ((byte >= 0x0A) && (byte <= 0x0F))
    {
        return (mb_char_t)(byte - 0x0A + 'A');
    }

    return '0';
}

/**
  \brief  This function will copy memory content from source address
          to destination address.
*/
void *modbus_memcpy(void *dst, const void *src, mb_uint32_t count)
{
    mb_char_t *tmp = (mb_char_t *)dst, *s = (mb_char_t *)src;
    mb_uint32_t len;

    if (tmp <= s || tmp > (s + count))
    {
        while (count--)
            *tmp ++ = *s ++;
    }
    else
    {
        for (len = count; len > 0; len--)
            tmp[len - 1] = s[len - 1];
    }

    return dst;
}

/**
  \brief  This function will set the content of memory
          to specified value.
*/
void *modbus_memset(void *s, mb_int32_t c, mb_uint32_t count)
{
    mb_char_t *xs = (mb_char_t *)s;

    while (count--)
        *xs++ = c;

    return s;
}

/**
  \brief  Return the length of a string, which terminate will
          null mb_char_tacter.
*/
mb_size_t modbus_strlen(const mb_char_t *s)
{
    const mb_char_t *sc;

    for (sc = s; *sc != '\0'; ++sc); /* nothing */
    return sc - s;
}

/**
  \brief  Sets many bits from a single byte value (all 8 bits of the byte
          value are set).
*/
void modbus_set_bits_from_byte(mb_uint8_t *dest,
    mb_int32_t idx, const mb_uint8_t value)
{
    mb_int32_t i;
    for (i = 0; i < 8; i++)
    {
        dest[idx + i] = (value & (1 << i)) ? 1 : 0;
    }
}

/**
  \brief  Sets many bits from a table of bytes (only the bits between
          idx and idx + nb_bits are set).
*/
void modbus_set_bits_from_bytes(mb_uint8_t *dest, mb_int32_t idx,
    mb_uint32_t nb_bits, const mb_uint8_t *tab_byte)
{
    mb_uint32_t i;
    mb_int32_t shift = 0;

    for (i = idx; i < idx + nb_bits; i++)
    {
        dest[i] = tab_byte[(i - idx) / 8] & (1 << shift) ? 1 : 0;
        /* gcc doesn't like: shift = (++shift) % 8; */
        shift++;
        shift %= 8;
    }
}

/**
  \brief  Gets the byte value from many bits.
          To obtain a full byte, set nb_bits to 8.
*/
mb_uint8_t modbus_get_byte_from_bits(const mb_uint8_t *src,
    mb_int32_t idx, mb_uint32_t nb_bits)
{
    mb_uint32_t i;
    mb_uint8_t value = 0;
    
    if (nb_bits > 8)
    {
        /* Assert is ignored if NDEBUG is set */
//      assert(nb_bits < 8);
        nb_bits = 8;
    }
    for (i = 0; i < nb_bits; i++)
    {
        value |= (src[idx + i] << i);
    }
    return value;
}

/**
  \brief  Get a float from 4 bytes (Modbus) without any conversion (ABCD)
*/
mb_float_t modbus_get_float_abcd(const mb_uint16_t *src)
{
    mb_float_t f;
    mb_uint32_t i;
    i = _ntohl(((mb_uint32_t)src[0] << 16) + src[1]);
    modbus_memcpy(&f, &i, sizeof(mb_float_t));
    return f;
}

/**
  \brief  Get a float from 4 bytes (Modbus) in inversed format (DCBA)
*/
mb_float_t modbus_get_float_dcba(const mb_uint16_t *src)
{
    mb_float_t f;
    mb_uint32_t i;
    i = _ntohl(_bswap_32((((mb_uint32_t)src[0]) << 16) + src[1]));
    modbus_memcpy(&f, &i, sizeof(mb_float_t));
    return f;
}

/**
  \brief  Get a float from 4 bytes (Modbus) with swapped bytes (BADC)
*/
mb_float_t modbus_get_float_badc(const mb_uint16_t *src)
{
    mb_float_t f;
    mb_uint32_t i;
    i = _ntohl((mb_uint32_t)(_bswap_16(src[0]) << 16) + _bswap_16(src[1]));
    modbus_memcpy(&f, &i, sizeof(mb_float_t));
    return f;
}

/**
  \brief  Get a float from 4 bytes (Modbus) with swapped words (CDAB)
*/
mb_float_t modbus_get_float_cdab(const mb_uint16_t *src)
{
    mb_float_t f;
    mb_uint32_t i;
    i = _ntohl((((mb_uint32_t)src[1]) << 16) + src[0]);
    modbus_memcpy(&f, &i, sizeof(mb_float_t));
    return f;
}

/**
  \brief  DEPRECATED - Get a float from 4 bytes in sort of Modbus format
*/
mb_float_t modbus_get_float(const mb_uint16_t *src)
{
    mb_float_t f;
    mb_uint32_t i;
    i = (((mb_uint32_t)src[1]) << 16) + src[0];
    modbus_memcpy(&f, &i, sizeof(mb_float_t));
    return f;
}

/**
  \brief  Set a float to 4 bytes for Modbus w/o any conversion (ABCD)
*/
void modbus_set_float_abcd(mb_float_t f, mb_uint16_t *dest)
{
    mb_uint32_t i;
    modbus_memcpy(&i, &f, sizeof(mb_uint32_t));
    i = _htonl(i);
    dest[0] = (mb_uint16_t)(i >> 16);
    dest[1] = (mb_uint16_t)i;
}

/**
  \brief  Set a float to 4 bytes for Modbus with byte and word swap conversion (DCBA)
*/
void modbus_set_float_dcba(mb_float_t f, mb_uint16_t *dest)
{
    mb_uint32_t i;
    modbus_memcpy(&i, &f, sizeof(mb_uint32_t));
    i = _bswap_32(_htonl(i));
    dest[0] = (mb_uint16_t)(i >> 16);
    dest[1] = (mb_uint16_t)i;
}

/**
  \brief  Set a float to 4 bytes for Modbus with byte swap conversion (BADC)
*/
void modbus_set_float_badc(mb_float_t f, mb_uint16_t *dest)
{
    mb_uint32_t i;
    modbus_memcpy(&i, &f, sizeof(mb_uint32_t));
    i = _htonl(i);
    dest[0] = (mb_uint16_t)_bswap_16(i >> 16);
    dest[1] = (mb_uint16_t)_bswap_16(i & 0xFFFF);
}

/**
  \brief  Set a float to 4 bytes for Modbus with word swap conversion (CDAB)
*/
void modbus_set_float_cdab(mb_float_t f, mb_uint16_t *dest)
{
    mb_uint32_t i;
    modbus_memcpy(&i, &f, sizeof(mb_uint32_t));
    i = _htonl(i);
    dest[0] = (mb_uint16_t)i;
    dest[1] = (mb_uint16_t)(i >> 16);
}

/**
  \brief  DEPRECATED - Set a mb_float to 4 bytes in a sort of Modbus format!
*/
void modbus_set_float(mb_float_t f, mb_uint16_t *dest)
{
    mb_uint32_t i;
    modbus_memcpy(&i, &f, sizeof(mb_uint32_t));
    dest[0] = (mb_uint16_t)i;
    dest[1] = (mb_uint16_t)(i >> 16);
}

